Union City is a city in the northern part of Hudson County, in the U.S. state of New Jersey. As of the 2020 United States census, the city was the state's 18th-most-populous municipality, with a population of 68,589, an increase of 2,134 (+3.2%) from the 2010 census count of 66,455, which in turn had reflected a decline of 633 (−0.9%) from the 67,088 counted in the 2000 census. As of the 2010 Census, among cities with a population of more than 50,000, it was the most densely populated city in the United States, with a density of 54,138 per square mile of land. The Census Bureau's Population Estimates Program calculated that the city's population was 65,366 in 2022, ranking the city the 590th-most-populous in the country.

North Hudson is the area in the northern part of Hudson County, New Jersey, situated on the west bank of the Hudson River, mostly atop the Hudson Palisades. It comprises Weehawken, Union City, West New York, Guttenberg, and North Bergen.